4 Why am I participation on this Seminar Series?The VisionI want to make impact on society.Engineering is key to a better future for humans and our environment.The ProblemLow engineering enrolments nationwide.Alarming enrolment trends.Most teachers do not have engineering background.A Possible solutionWhen incoming students are aware about engineering is, they are likely to choose it.Educate teachers about engineering.

16 Electrical and Computer Engineering“Electrical engineering is an engineering discipline that deals with the study and/or application of electricity, electronics and electro-magnetism.”“Computer engineering is a discipline that combines elements of both electrical engineering and computer science. Computer engineers are involved in many aspects of computing, from the design of individual microprocessors, personal computers, and supercomputers, to circuit design.”Easier to understand by exploring example systems

24 Future ECE Job Prospects*Computer hardware engineers are expected to have employment growth of 4 percent over the projections decade, for all occupations. Although the use of information technology continues to expand rapidly, the manufacture of computer hardware is expected to be adversely affected by intense foreign competition. As computer and semiconductor manufacturers contract out more of their engineering needs to both domestic and foreign design firms, much of the growth in employment of hardware engineers is expected to take place in the computer systems design and related services industry.Electrical engineers are expected to have employment growth of 2 percent over the projections decade. Although strong demand for electrical devices including electric power generators, wireless phone transmitters, high-density batteries, and navigation systems should spur job growth, international competition and the use of engineering services performed in other countries will limit employment growth. Electrical engineers working in firms providing engineering expertise and design services to manufacturers should have better job prospects.Electronics engineers, are expected to experience little to no employment change over the projections decade. Although rising demand for electronic goods including communications equipment, defense-related equipment, medical electronics, and consumer products should continue to increase demand for electronics engineers, foreign competition in electronic products development and the use of engineering services performed in other countries will limit employment growth. Growth is expected to be fastest in service-providing industries particularly in firms that provide engineering and design services.*Bureau of Labor & Statistics

28 Direct Current (DC) & Alternating Current (AC)Current that is constant with timeFor examples, I=3A or V=12VACCurrent that varies with time and reverses its direction periodically (sinusoidal)For example,Thomas Edison(1847 – 1931)Nikola Tesla(1856 – 1943)

29 Water-Model Analogy We cannot see electric current flowing in a wireWater-model or fluid-flow analogy helps us visualize the behaviors of electrical circuits and elementsElectric Current = flow of electrical charges(Water) Current = flow of water moleculesAssumptionsFrictionless pipesNo gravity effectIncompressible wateri(t)wire / pipecross section

31 Voltage Voltage Water models Measured between two points (terminals)Energy transferred per unit of charge that flows from one terminal to the otherIntuitive interpretations: potential difference, water pressure in water modelVariable:Unit: volt [V]Water modelsFor constant voltage sourcesConstant-pressure water pumpConstant-torque motorAlessandro Volta(1745 – 1827)

32 Rules of Current Flow - Kirchhoff’s Current LawKirchhoff’s current law (KCL)Conservation of electrical currentsThe sum of all the currents into a node is zeroThe sum of the currents entering a node equals the sum of the currents leaving a nodeGustav Kirchhoff(1824 – 1887)node

33 Rules of Current Flow - Kirchhoff’s Voltage LawKirchhoff’s voltage law (KVL)Conservation of energyThe sum of the voltages around any closed path (loop) is zeroExampleloop 31539+_124loop 1loop 2

34 CKT Components - The ResistorElectrical component that resists the current flowVariable: R [ohm] orWater models for a resistorRconstrictionRRsponge=~

43 CKT Components - The InductorStores energy through storing magnetic fieldConstruction: coiling a wire around some type of formVariable: L [Henry] or [H].When the electric current changes in the coil, it creates a magnetic field around the wire which induces voltage across the coil+_LJoseph Henry( )

44 CKT Components - The Inductor (cont’d)OperationWhen the electric current changes in the coil, it creates a magnetic field around the wire which induces voltage across the coilWater model analogyBi-directional turbine driving a flywheelPassive, driven by current; no motorMomentum

67 The Digital Audio StreamA series of sample numbers, to be interpreted as instantaneous amplitudesone number for every tick of the sample clockFrom previous example:This is what appears in a sound file, along with a header that indicates the sampling rate, bit depth and other thingsEach number is then converted to binary and stored in a register

69 Digital Technology: DVDDigital Versatile Disc or Digital Video DiscFirst appeared in the US market in March 1997Employ the same red laser as in CDsHigher-density multi-layer discs to improve storage capacityDVD Audio: 192-kHz 24-bit sampling rate!

87 Cell PhoneA cell phone is a very complex system that can receive input signals in various forms (electromagnetic waves from base station, sound from microphone, text from key pad) and convert them to several desired types of output signals (sound through speaker, electromagnetic waves to base station, graphics to screen)

90 Sound Fundamentals Sound waves: vibrations of air particlesFluctuations in air pressure are picked up by the eardrumsVibrations from the eardrums are then interpreted by the brain as sounds

91 Harmonics in Music SignalsThe spectrum of a single note from a musical instrument usually has a set of peaks at harmonic ratiosIf the fundamental frequency is f, there are peaks at f, and also at (about) 2f, 3f, 4f…Best basis functions to capture speech & music: cosines & sines

102 The Cell ApproachCellular telephone system is based on the principle of radio communicationCoverage area is divided into hexagonal cells (each covers around 10 square miles)Non-adjacent cells can reuse the same frequenciesLow-power transmitters: both phones & base stationsEach city has a Mobile Telephone Switching Office (MTSO)Each carrier: 832 radio frequenciesDuplex system: 395 voice channels & 42 control channelsEach cell: 56 voice channels

103 From Cell to CellSystem Identification (SID) code to check for available serviceMTSO uses the control channels to identify where the user is & assign frequenciesMTSO handles the hand-off switching between cells based on signal strengthsEverything happens within seconds or even less!

104 Switching, RF and Power ElectronicsCell Phone TowerAntenna ArraySwitching, RF and Power Electronics

105 What Next? Connect & collaborate with UMass Amherst ECE facultyTeacher development grantsSummer research experience for teachersRecommend exceptional high-school juniors/seniors summer research at UMass.Invite UMass Profs to High-school student seminars.M5 Open house for students and Teachers.Spread the word to students & colleagues.Participate on upcoming ECE SESS(more in-depth).Marinos N. Vouvakis

106 DisclaimerSome materials (drawings, figures, text) presented in these slides was obtained from the following web resources: